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Posted: 4/12/2002 1:20:50 PM EDT
big deal about head space in assembling a new upper ???

stop me if i am wrong, there is only one way to insert the barrel into the bare upper, right ? you can grip the barrel wyth special vise jaws or a receiver clamp which also fits into a vise, right ? you then tighten the barrel nut assy. till it is very "snug",(abt. 20 ftlbs) then tighten till the notches for the gas tube aligns,(abt. 35 ftlbs) that is usually not more than one or two notches past "very snug", drop in a fully assembled new bolt carrier wyth new bolt, place an unfired round in the chamber & push the BC forward wyth thumb, bolt shud lock up on cartridge wyth a small force, thats good !! if it takes stiff resistance wyth thumb to lock it, thats OK, the head space will "wear in" wyth "break in", the head space is only "BAD" if you can not lock the bolt on an unfired round wyth thumb pressure alone.., this requires a chamber reamer fix !! or return the barrel.......

just keep in mind that if your bolt does NOT lock up on a factory made round, you got problems !!!!!!!!!!!

Link Posted: 4/12/2002 2:17:44 PM EDT
do you have a problem spelling 'WITH'? Just Curious.

Headspace is important for proper function, and positive lockup. Also for avoiding the KB factor.

Link Posted: 4/12/2002 2:34:28 PM EDT
"curosity killed a cat"

i was told a few tymes when i was a mere child.........

YES !! no kidding ?? where did i say it is NOT important ?? i just gave what i belive is a quick check for the new builders who seem to shy away from building an upper for the reason that they are "afraid" to because of that nasty ol headspace problem........
Link Posted: 4/12/2002 3:19:26 PM EDT
Headspace is feined as a measurement taken from the face of the bolt to a reference point in the chamber. The minimum and maximum headspace measurements are fixed to certain tolerances. If you measure headspace witha live cartridge you are not necessarily within those tolerances as there is a larger tolerance range for ammo so that it will chamber in minum (match) and maximum (field) chambers. Chamber reamers are not always sharp and the same reamer will cut a different chamber when it is dull as compared to being sharp. If headspace is insufficient (bolt will not fully close on a 'GO' gauge) then a chamber reamer may fix it. If heaspace is excessive (bolt will close on a 'NO GO' gauge) a chamber reamer will ceratinly not fix it unless the barrel is set back. The difference between minimum and maximum headspace dimensional tolerances is from 0.003 to 0.004 thousnadths of an inch. That is the thickness of a single sheet of 8 1/2 x 11 inch papaer. Do you really believe it should not be checked or is not a big deal? JarheadGunner.
Link Posted: 4/12/2002 3:21:56 PM EDT
Headspace is defined as a measurement taken from the face of the bolt to a reference point in the chamber. The minimum and maximum headspace measurements are fixed to certain tolerances. If you measure headspace witha live cartridge you are not necessarily within those tolerances as there is a larger tolerance range for ammo so that it will chamber in minimum (match) and maximum (field) chambers. Chamber reamers are not always sharp and the same reamer will cut a different chamber when it is dull as compared to being sharp. If headspace is insufficient (bolt will not fully close on a 'GO' gauge) then a chamber reamer may fix it. If heaspace is excessive (bolt will close on a 'NO GO' gauge) a chamber reamer will ceratinly not fix it unless the barrel is set back. The difference between minimum and maximum headspace dimensional tolerances is from 0.003 to 0.004 (thousandths) of an inch. That is the thickness of a single sheet of 8 1/2 x 11 inch paper. Do you really believe it should not be checked or is not a big deal? JarheadGunner.
Link Posted: 4/12/2002 9:49:05 PM EDT
Look a few forum topics down at the really big MIa ka- boom and ask your self this question, will i be this lucky(if you call the total distruction of a rifle) if this happens because of poor head-spacing? bob cole
Link Posted: 4/13/2002 1:02:22 PM EDT
bobby ol buddy,

we're talking AR15 here..., M1a is a totaly different puppy........

Link Posted: 4/13/2002 1:12:09 PM EDT
JHG,

i agree wyth what you say.........BUT !!

AR's are a whole lot different than most other guns, i have read right here on these forums, where "Jarheads" formed an "assembly" line type cleaning of their M16's, one person/group done all the bolt carriers & bolts...etc., when it come tyme to assemble the rifles, no one knew which part went wyth which upper or lower or what..., & they worked !!

in essence, what i am saying is that a properly assembled AR16 wyth quality parts will not have a headspace problem.........

where in AZ. are you ?



Link Posted: 4/13/2002 2:44:02 PM EDT
CJ - When you drop a hammer on a chambered round in a properly mounted rifle, you are, holding a 50,000 PSI 'pipe bomb' next to your head. Do you really want a cartridge case to fail because it may be stretched beyond its' e;astic limits in an chamber with excessive headspace? I agree with you that a properly assembled AR with quality parts should not have a headspace problem. However, the operative term is 'should'. Military rifles have a rigorous inspection process before acceptance. Civilian rifles, especially parts guns, may have been assembled with mil-spec parts that have been rejected by the military because they did not meet the tolerance limits required for acceptance. Witness all of the cheap parts available at gun shows/flea markets. Therefore, I check the headspace on every AR and other fireearm I work on, and, I work on many. I have found headspace to be an issue by experience. I am a retired Jarhead and I may be one of those who cleaned rifles and mixed parts. Headspace was checked with a field gauge, at a minimum, after such sessions. I am in Prescott - where are you? JarheadGunner.
Link Posted: 4/13/2002 3:06:18 PM EDT
Link Posted: 4/13/2002 7:55:08 PM EDT
very good information from both of you, JHG & Troy.........

i do plan to continue using a "no go" gage, but when Duncan Long & others do not factor in or fail to emphasize it's importance in their books i see it as not being a big problem.....

JHG,
i am in Tucson, our new rifle range shud be ready to use this week, looking forward to burning up a bunch of powder......
Link Posted: 4/14/2002 7:24:19 AM EDT
New rifle range? I briefly lived in the Tucson area, Catalina actually, about 10 years ago. I occasionally shot at the range in 3 Points. Used to stop at 'Tinys' for a steerburger on the way back. Tucson is a great place, but, the weather was just too hot for me in the summer. Where is your new range? Maybe I can break away and shoot there some time. Take care. JarheadGunner.
Link Posted: 4/14/2002 11:20:58 AM EDT
Checking the headspacing of a brand new upper is just basically checking the work of the guy who installed the extension on the barrel and did the chambering. If it's someone you trust with your life, fine. No need to check.

If not, by all means check. It isn't rocket science
Link Posted: 4/14/2002 12:17:58 PM EDT
JHG,

Desert Trails Gun Club 7777 E. Valencia , coming down I-10 from PHX, take the Valencia Rd. exit & go east about 5 or 6 miles......

the pistol & rifles that fire pistol rounds range is open now, has been for a year, i am having a hard tyme convincing the owner that my 1" bore cannon is just a big pistol, because it has a pistol grip.......!!


NormG,
good advice !!!!!
Link Posted: 4/14/2002 4:43:22 PM EDT
CJ - my in-laws live in Nogales, AZ. I have to go down that way soon to deal with a death in the family and such. I will try to check out the range and perhaps we can meet there and shoot one day soon. Does the range have a metallic silhouette set up? Take care. JarheadGunner.
Link Posted: 4/14/2002 10:18:41 PM EDT

Originally Posted By bobbyjack:
Look a few forum topics down at the really big MIa ka- boom and ask your self this question, will i be this lucky(if you call the total distruction of a rifle) if this happens because of poor head-spacing? bob cole



I never said that!!!!!!!!!
Link Posted: 4/15/2002 5:47:35 AM EDT
we know that !! it was someone else.............
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